Drying apparatus

ABSTRACT

The invention concerns drying apparatus suitable for drying strip material, which comprises a drying chamber through which strip material may be passed, a strip entrance and exit aperture in the chamber to allow passage of strip material into and out of the drying chamber, a plurality of rotatable support rolls being disposed in parallel and spaced apart relationship to define a cylindrical cage within the chamber and over which strip material may be passed, means cooperating with the rolls of the cage to enable strip material passing thereover to be supported by a part of the peripheral surface of each roll of the cage and drying means for drying strip material passing over the rolls of the cage.

ited States Patent ansen Aug. M, 1973 [54] DRYKNG APPARATUS 3,638,3302/1972 Stout 34/156 l Wtier- [75] Inventor E2? Ernst nansenlmgen SPnmary Examiner-Carroll B. Donty, .lr. WW H W Assistant E qminer Larr yl. c&u arta V [73 Assignee: Multitec A. (1., Canton of Berne, Attoreys-1 F. Obkm Irwln McClelland Switzerland l l;

221 Filed: Dec. 7, 1971 [57] 11 [211 App]. No.: 205,505 The inventionconcerns drying apparatus suitable for drying strip material, whichcomprises a drying chamher through which strip material may be passed, astrip [30] Applisafion pfiority Data entrance and exit aperture in thechamber to allow pas- Dec. 9, 1970 Switzerland 18226 sage of stripmaterial into and out of the drying cham her, a plurality of rotatablesupport rolls being disposed [52] US. Cl. 34/155, 34/160 in parallel andSpaced apart relationship to define a [51] Int. Cl. F26b 9/00 lindrisalcage within the chamber and over which strip [58] Field of Search34/115, 155, 122, material may be passed, means cooperating with the34/160 240 rolls of the cage to enable strip material passing thereoverto be supported by a part of the peripheral surface References Cited ofeach roll of the cage and drying means for drying UNITED STATES PATENTSstrip material passing over the rolls of the cage.

44,402 9/1864 Cummings et a1 34/155 1.1.; 703,044 6/1902 Crowell 34 15510 C 10 Drawing Fawn-es 772,694 10/1904 Crowell 34/155 2,624,573 l/1953Rice 34/155 PAIENIEB AUG] 4 1915 saw 2 or 3 DRYING APPARATUS BACKGROUNDOF THE INVENTION 1. Field of invention The present invention relates todrying apparatus, and more specifically to apparatus suitable for dryingcoatings on strip material,particularly on paper and foil.

2. Description of the Prior Art Apparatus for coating and drying stripmaterial have been known for some time. For drying, hot air-jet driersoptionally in combination with IR. irradiation heaters, have beenemployed.

Many coatings are often required on one or both sides of the stripmaterial, especially in the paper and foil manufacturing industry andalso in the production of light sensitive reproduction materials,wherein it is desirable that one coating be completely dry before thenext coating is applied. During the drying operation, physical contactwith a freshly applied coating is clearly to be avoided.

in the known apparatus, the coated strip material, with the freshlycoated side facing upwards, is led through a drying chamber in such away that the dry underside is lead over support rolls, which rolls maybe driven or freely rotatable. However, it is often observed with stripmaterial, particularly paper, that when damp, the strip tends to curl inalong the edges and become distorted, whereby longitudinal folding ofthe strip is prone to occur. This tendency is greater the smaller thesupporting surface on the peripheral surface of each support roll andthe greater the distance between the supporting rolls. It is possible toincrease the supporting surface of each roll by directing the stripmaterial through a large angle around the roll. However, this results inlarger distances between support rolls. In known drying apparatus, thesedisadvantages have been reduced or avoided by arranging the rolls of thedrying chamber in the form of an arc and by employing small diametersupporting rolls in close together relationship.

In order to provide for continuous coating involving a plurality ofcoats with associated intermediate and final drying of the coats, two ormore of such drying chambers as herinbefore described and having strippaths of arcuate form have been used in one-above-theother relationship.On each side of at least the first drying chamber, a coating means hasbeen arranged together with a system of rolls for directing the stripfrom one drying chamber to the other. Generally, the strip materialpasses under a first coating means wherein a coating is applied to oneside thereof and thence through a first drying chamber having rollsarranged as hereinbefore described. The strip material then passes to asystem of rolls wherein it is directed to a second coating means whereina coating is applied to the other side of the strip and thence to asecond such drying chamber. By this means, coating and drying of thecoating, on each side is possible. By analogous means, it is possible todirect the strip material such that the second coating is applied to thedry first coated side and theoretically, it is also possible to directthe strip material such that a plurality of coats are applied to bothsides of the strip material. However, since the strip material cannotcross itself and cannot be supported on a freshly coated side, such anarrangement becomes 2 complicated, space consuming and generallyimpractical.

Another known form of coating and drying apparatus has many dryingchambers arranged lying in a plane, coating means being provided aheadof each drying chamber. The drying chambers in such an apparatuscomprise a series of rolls, the axes thereof being arranged in a plane.By directing the coated and dried strip material by means of anappropriate system of rolls, it is possible to program the coatings toachieve consecutive coatings on one side, or alternately on each side,intermediate dryings being effected between coatings. it is clear thatsuch an arrangement has the disadvantage that a large amount of groundspace is required because of the planar arrangement of drying chambersand intermediate strip directioning roll systems, and also thedisadvantages abovementioned associated with the lack of support oflinearly arranged rolls within the drying chambers causing curling anddistortion of the strip material and leading to longitudinal foldingthereof.

Furthermore both of the aforementioned known drying apparatus exhibit afurther disadvantage when employing hot air-jet heaters. It is arequirement in drying strip material by means of hot air-jet heatersthat the air jet flow and also that the resulting part-saturated airflow be evenly distributed over the surface of the strip. One generalmethod of satisfying this requirement is by employing a partially sealedair circulation system whereby some of the part-saturated exhaust air isdischarged to the atmosphere and the system is replenished with freshair, the mixture being heated up in a heater and led to the nozzles ofthe hot air jet drier. It is established technically that to obtain anabsolutely even flow pattern in flat or circular chambers of rectangularcross-section such that no air congestion, resulting in zeroflow,occurs, is extremely difficult. it is also established that wetting of,e.g. paper strip, in a coating process, causes curling of the edges andthat this phenomenon is reversed during drying so that the edges curltowards the uncoated side. As the supporting rolls are disposed underthe uncoated side of the strip material, it will be appreciated thatthere is a great danger of the curled underside of the strip gettingsquashed between the strip itself and the rolls. This problem isparticularly applicable to drying chambers of planer construction sincethere is minimal supporting surface beneath the strip material and alsoair congestion zones of zero net air flow tend to be caused.

To avoid the abovementioned disadvantages, different proposals have beenput forward, e.g. by a complicated arrangement of the jets, all of whichare complex, expensive and are not capable of general application.

SUMMARY OF THE llNVENTlON It is an object of the present invention toprovide a drying apparatus which may be employed in conjunction withknown coating means to overcome or substantially to reduce theaforementioned disadvantages.

Accordingly, the present invention provides a drying apparatus suitablefor drying coated strip material, which comprises a. a drying chamberthrough which strip material may be passed,

b. means defining a strip entrance and exit aperture in the dryingchamber to allow passage of strip material into and out of the dryingchamber,

c. a series of support rolls being disposed in parallel and spaced apartrelationship to define a cylindrical cage within the chamber and overthe rolls of which, strip material may be passed,

d. means cooperating with the rolls of the cage to enable strip materialpassing thereover to be supported by a portion of the peripheral surfaceof each roll of the cage, and

e. drying means for drying strip material passing over the rolls of thecage.

Preferably, the drying means is a hot air-jet drier comprising aplurality of nozzles arranged in a cylindrical surface within the dryingchamber radially outwardly of the cage and directed radially inwardly,an air outlet pipe extending from the drying chamber, an air inlet pipefor conducting hot air to the nozzles, an air heater for heating the airbefore passage thereof through the air inlet pipe, an air pump forpumping air to the air heater, and an air connecting pipe through whichair may pass from the pump to the heater. In addition, the air outletpipe may be connected to the pump such that some at least of the airpassing from the drying chamber through the outlet pipe is recycledthrough the inlet pipe. Generally, it is preferred that the nozzlecomprise slits extending axially in the radially inner surface of ahollow cylindrical jacket, the air inlet pipe communicating with thejacket.

The drying apparatus of the invention may be employed in conjunctionwith any known coating means, e.g. a coating roll and an air brush withthe associated counter roll.

The cylindrical arrangement of the supporting rolls allows the advantageof a circular strip material path through the drying apparatus and overthe support rolls,allowing on the one hand extremely satisfactorysupport of the strip material on the support rolls, whereby the dangersof distortion and longitudinal curling and folding are much reduced, andon the other hand much reduced ground space, e.g. in an apparatusenabling one or two coats to be applied and dried, the length of theapparatus as compared to the length of known apparatus of similarcapacity is reduced to as much as one third of that length.

As opposed to drying chambers having rollers arranged in linear orarcuate formation, the strip material is led into and passes out of thesame aperature in the drying chamber. In the case where hot air-jetdrying means are employed, the arrangement of the nozzles to be directedradially inwardly overcomes or substantially reduces the hereinbeforedisadvantages of air congestion and zones of zero air flow, the hot airbeing supplied and distributed over the whole periphery of the strip andflowing evenly against the strip.

Drying and coating apparatus may incorporate any number of units ofdrying apparatus constructed in ac cordance with the present invention.Generally, three such units are found to be convenient wherein eightvariations with respect to the number and sequence of coatings ispossible. Naturally, the number of drying apparatus units employed willdepend on the particular requirements and may be either increased ordecreased as circumstance demands.

In the case wherein the drying apparatus of the present invention isprovided with its own air circulation and heating system, this has theadvantage that in a coating and drying apparatus embodying more than oneheating unit, individual heating temperatures can be set by thermostaticregulation allowing the inlet and outlet air temperatures to becontrolled automatically.

Further objects and advantages will appear from the followingdescription of a preferred embodiment of the invention, and the novelfeatures will be particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, part-sectionalview of a drying apparatus of the preferred embodiment,

FIG. 2 is a schematic sectional view along the line A-A of FIG. 1, and

FIGS. 3 to 10 are diagrammatic views of various coating and dryingapparatus incorporating at least one of the drying apparatus of thepreferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, identical partsbear identical reference numerals.

The drying apparatus of the preferred embodiment shown in detail inFIGS. 1 and 2, comprises a drying chamber 4. Mounted within the dryingchamber 4 are a series of support rolls 3 disposed in parallel andspaced apart relationship to define a cylindrical cage, shown moreclearly in FIG. 2. Radially outwardly of the cage, and embodying part ofthe wall of the drying chamber is a hollow cylindrical jacket 7 providedon the radially inner wall thereof with a plurality of slits 5 extendingaxially across virtually the length of the wall, these slitsconstituting hot air-jet nozzles and being directed radially inwardly.An aperture, in the form of a slot, in the drying chamber 4 and jacket 7allows communication of the roll cage with the exterior to permitpassage of strip material 2 into and out of the chamber. The lengths lof strip material entering and leaving the drying chamber 4 is shown inFIG. 2 A nip roll 20 cooperating with the terminal roll of the roll cageadjacent the slot serves to enable the strip material to be supportedover substantially the whole length thereof by the roll cage. Along theaxis or the roll cage extends an air outlet pipe 8 which projects a partway into the chamber 4, and runs from the chamber 4 to a pump 10. Theend 9 of the outlet pipe 8 may be disconnected from the pump 10. Thepump 10 is connected to an air heater 12 by means of a connecting pipe11. Running off the connecting pipe 11 is a discharge duct 14 providedwith a butterfly valve 15. The air heater is connected to the jacket 7by means of an air inlet pipe 13 which is connected to the chamber 4 atjunction 6. In one end face of the chamber 4, opposite the mouth of theoutlet pipe 8 and lying along the axis of the roll cage is an air inletaperture 16 provided with valve means in the form of a grid of parallelshutters of adjustable inclination.

The operation of the drying apparatus of the preferred embodiment willnow be described.

Freshly coated strip material 2 is led into the drying chamber throughthe slot therein, around the roll cage between nip roll 20 and theterminal roll of the roll cage and out again through the slot in thedrying chamber.

I-Iot air is fed to the jacket 7 through inlet pipe 13 from heater 12.The hot air is distributed generally evenly around the jacket 7 and isthen forced through the slits 5 to impinge on the continuously movinglength of strip material 2. Partially saturated air travels generallyradially inwardly of the chamber 4 and the vortex so formed around theprojecting mouth of the outlet pipe 8 is sucked out through the outletpipe 8 to the pump. Some of this same air passes from the pump throughthe connecting pipe 11 to the heater 12 to be once more cycled throughthe system. However, a certain proportion of this air is dischargedthrough the discharged duct M into the atmosphere. The amount of airdischarged in this manner may be controlled by adjustment of thebutterfly 15. Pressure in the drying chamber may be restored byadmittance of air through the air inlet aperture 16, and a balance maybe achieved by adjustment of the shutter inclination thereof. It will beappreciated that a condition of balance may be achieved with relativeease whereby all air discharged through discharge duct 14 is replenishedby air entering through the shutter grid of the air inlet aperture 16.In this condition, substantially no air is lost through the strip inletand outlet slot in the drying chamber such that all air flow isgenerally evenly distributed radially inwardly of the chamber.

The above described air circulation system has the advantage that bysuitable adjustment of the shuttersof aperture 16 and butterfly 15, suchthat no net flow of air takes place through the strip material inlet andoutlet slot in the drying chamber, the aerodynamic flow pattern withinthe drying chamber is substantially symmetrical and even.

The above described air circulation and drying system is applicable tothe drying of water-based coatings. When it is desired to dry outcoatings based on other solvents or supporting media, the end 9 of theair outlet pipe is sealed to prevent air outlet, and the inlet to thepump is opened to the atmosphere. The butterfly 15 is closed and theshutters of aperature l6 opened. If desired the aperture 16 is connectedto a condenser (not shown). In use,air from the atmosphere is passedinto the drying chamber via inlet pipe 13 and part saturated air passesout of the chamber through aperture 16 wherein, when a condenser isfitted, solvent may be removed from the outgoing air.

In a modification of the drying apparatus of the above describedembodiment, an alternative strip material inlet and outlet slot in thedrying chamber is also provided in the other side thereof as shown inthe broken line FIG. 2. For this purpose nip roll a is required,operating in an analogous manner to nip roll 20 hereinbefore described.

To illustrate the utility of the drying apparatus of the preferredembodiment, coating and drying apparatus embodying as a unit or unitsthe above described drying apparatus will now be described withreference to FIGS. 3 to 10.

Strip take off reels 18 are arranged to allow strip material 2 to be fedto a coating means 17 and via a drying apparatus to a take up reel 19.More than one coating means 17 and drying apparatus units may beemployed.

The coating and drying apparatus shown in FIGS. 9 and 10 illustrated themanner in which a system comprising three drying apparatus units may bearranged to coat and dry coatings and the coating possibilities of suchan apparatus.

FIGS. 3 and 4 show a path of strip material suitable for applying anddrying a coating on one side only of the strip material;

FIG. 5 shows a path of strip material suitable for applying and dryingtwo coatings on one side only of the strip material;

FIG. 7 shows a path of strip material suitable for applying and dryingthree coatings on one side only of the strip material;

FIG. 6 shows a path of strip material suitable for applying and dryingone coating on each side of the strip material; and

FIGS. d, 9 and 10 show a path of strip material suitable for applyingand drying two coatings on one side and one coating on the other side ofthe strip material.

Whilst the preferred form of the present invention has been described,changes and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of theinvention.

What is claimed is:

l. Drying apparatus suitable for drying coated strip material whichcomprises a. a drying chamber through which strip material may bepassed,

b. means defining a strip entrance and exit aperture in the dryingchamber to allow passage of strip material into and out of the dryingchamber,

0. A series of support rolls being disposed in parallel and spaced apartrelationship to define a cylindrical cage within the chamber and overthe rolls of which strip material may be passed,

d. means cooperating with the rolls of the cage to enable strip materialpassing thereover to be supported by a portion of the peripheral surfaceof each roll of the cage, and

e. hot air jet drying means for drying strip material passing over therolls of the cage comprising a plurality of nozzles arranged in acylindrical surface within the drying chamber radially outwardly of thecage and directed radially inwardly, an air outlet pipe having one endextending from the drying chamber and its other end extending into'thedrying chamber part way along the cylindrical axis of the cage, an airinlet pipe for conducting hot air to the nozzles, an air heater forheating the air before passage thereof through the air inlet pipe, anair pump for pumping air to the air heater and an air connecting pipethrough which air may pass from the pump to the heater.

2. The drying apparatus of claim I wherein the means cooperating withthe rolls of the cage comprises a nip roll cooperating with the terminalroll adjacent the means defining an aperture in the drying chamber andaround which nip roll strip material may be directed to pass out of thechamber.

3. The drying apparatus of claim 1 wherein said nozzles comprise slitsextending axially in the radially inner surface of a hollow cylindricaljacket, the air inlet pipe communicating with the jacket.

4. The drying apparatus of claim it wherein the air outlet pipe isconnected to the pump such that at least some of the air passing fromthe drying chamber through the outlet pipe is recycled through the inletpipe.

5. The drying apparatus of claim d wherein the drying means includes anair discharge pipe extending from said connecting pipe through whichsome of the air received from the pump may be discharged to theatmosphere and means defining an air inlet aperture in the dryingchamber disposed substantially opposite the mouth of the air outlet pipewithin the chamber and along the axis thereof.

6. The drying apparatus of claim wherein the discharge duct and meansdefining an air inlet aperture are each provided with valve means so asto enable control of discharge and inlet of air respectively.

7. The drying apparatus of claim 3 wherein the valve means in thedischarge duct is an adjustable butterfly valve.

8. The drying apparatus of claim 3 wherein the valve means in the meansdefining an air inlet aperture comprises a grid of parallel shutters ofadjustable inclination.

9. Coating and drying apparatus comprising the drying apparatus of claim1 in combination with at least one coating means. i I

10. Drying apparatus suitable for drying coated strip materialcomprising:

a drying chamber through which strip material may be passed;

an aperture in the drying chamber defining a common entrance and exitfor said strip material to allow passage of said strip material into andout of said drying chamber;

a series of support rolls being disposed in parallel and spaced apartrelation to define a cylindrical cage within said drying chamber andover the rolls of which said strip material may be passed;

means cooperating with the rolls of said cylindrical cage to enablestrip material passing thereover to be supported by a portion of theperipheral surface of each of the rolls of said cage; and

drying means for drying said strip material passing over the rolls ofsaid cylindrical cage comprising a plurality of hot air nozzles arrangedin a cylindrical pattern within said drying chamber radially outwardlyof said cylindrical cage and being directed radially inwardly; an airoutlet pipe from said drying chamber; and means for conducting hot airto said nozzles.

1. Drying apparatus suitable for drying coated strip material whichcomprises a. a drying chamber through which strip material may bepassed, b. means defining a strip entrance and exit aperture in thedrying chamber to allow passage of strip material into and out of thedrying chamber, c. A series of support rolls being disposed in paralleland spaced apart relationship to define a cylindrical cage within thechamber and over the rolls of which strip material may be passed, d.means cooperating with the rolls of the cage to enable strip materialpassing thereover to be supported by a portion of the peripheral surfaceof each roll of the cage, and e. hot air jet drying means for dryingstrip material passing over the rolls of the cage comprising a pluralityof nozzles arranged in a cylindrical surface within the drying chamberradially outwardly of the cage and directed radially inwardly, an airoutlet pipe having one end extending from the drying chamber and itsother end extending into the drying chamber part way along thecylindrical axis of the cage, an air inlet pipe for conducting hot airto the nozzles, an air heater for heating the air before passage thereofthrough the air inlet pipe, an air pump for pumping air to the airheater aNd an air connecting pipe through which air may pass from thepump to the heater.
 2. The drying apparatus of claim 1 wherein the meanscooperating with the rolls of the cage comprises a nip roll cooperatingwith the terminal roll adjacent the means defining an aperture in thedrying chamber and around which nip roll strip material may be directedto pass out of the chamber.
 3. The drying apparatus of claim 1 whereinsaid nozzles comprise slits extending axially in the radially innersurface of a hollow cylindrical jacket, the air inlet pipe communicatingwith the jacket.
 4. The drying apparatus of claim 1 wherein the airoutlet pipe is connected to the pump such that at least some of the airpassing from the drying chamber through the outlet pipe is recycledthrough the inlet pipe.
 5. The drying apparatus of claim 4 wherein thedrying means includes an air discharge pipe extending from saidconnecting pipe through which some of the air received from the pump maybe discharged to the atmosphere and means defining an air inlet aperturein the drying chamber disposed substantially opposite the mouth of theair outlet pipe within the chamber and along the axis thereof.
 6. Thedrying apparatus of claim 5 wherein the discharge duct and meansdefining an air inlet aperture are each provided with valve means so asto enable control of discharge and inlet of air respectively.
 7. Thedrying apparatus of claim 3 wherein the valve means in the dischargeduct is an adjustable butterfly valve.
 8. The drying apparatus of claim3 wherein the valve means in the means defining an air inlet aperturecomprises a grid of parallel shutters of adjustable inclination. 9.Coating and drying apparatus comprising the drying apparatus of claim 1in combination with at least one coating means.
 10. Drying apparatussuitable for drying coated strip material comprising: a drying chamberthrough which strip material may be passed; an aperture in the dryingchamber defining a common entrance and exit for said strip material toallow passage of said strip material into and out of said dryingchamber; a series of support rolls being disposed in parallel and spacedapart relation to define a cylindrical cage within said drying chamberand over the rolls of which said strip material may be passed; meanscooperating with the rolls of said cylindrical cage to enable stripmaterial passing thereover to be supported by a portion of theperipheral surface of each of the rolls of said cage; and drying meansfor drying said strip material passing over the rolls of saidcylindrical cage comprising a plurality of hot air nozzles arranged in acylindrical pattern within said drying chamber radially outwardly ofsaid cylindrical cage and being directed radially inwardly; an airoutlet pipe from said drying chamber; and means for conducting hot airto said nozzles.